• Composites Research
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• 제15권6호
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• pp.38-43
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• 2002

쾌속조형(Rapid Prototyping)기술은 다양한 형태치 재료를 사용하여 초기모형을 제작할 수 있다. Stratasys사의 FDM은 플라스틱 재료로 조형물을 제작하는 대표적인 쾌속조형공정이다. 또한 FDM으로 제작된 부품들은 하중을 받는 구조용 재료로도 사용된다. FDM은 약 300$\mu$m 두께의 가는 필라멘트의 형태의 일정한 방향으로 재료를 적층하므로, FDM으로 제작된 부품들은 이방성 재료의 성질을 나타낸다. 본 연구에서는 FDM 부품의 인장강도를 예측하기 위한 해석방법을 제시하고자 한다. 복합재를 위한 Classical Lamination Theory를 사용하여 컴퓨터 코드를 작성하였다. FDM 제품의 파괴를 예측하기 위하여 계산펀드에 Tsai-Wu failure criterion 이론을 도입하였다. 해석방법에 의해 예상되는 인장강도와 실제 실험으로 얼은 수치를 비교하였다. 예상치가 측정치에 근사한 값을 보이므로 본 계산식의 타당성이 입증되었다. 덧붙여서 FDM의 강도계산과 설계규칙이 웹기반의 제안서비스(FDMAS)에서 제공된다.

• 한국안전학회지
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• 제31권6호
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• pp.1-5
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• 2016

A bicycle is one of the most popular sporting goods in view of a sport activity and a human health. Metallic materials such as steel, aluminum, etc. were mainly used to the bicycle fork in the past. Nowadays, the carbon fiber reinforced composite materials are widely used to the manufacturing of a bicycle fork to reduce the weight and to increase the efficiency. Safety is a most important design parameter of a bicycle fork even if the weight and cost reduction are important. Bicycle failure may happen at the critical spot of a bicycle fork and cause the accident. In this paper, the composite bicycle fork will be analyzed to secure the safety and detect a critical spot by using the finite element method with Tsai-Wu failure criterion. The stress data were obtained for the laminated composites with various number of plies and fiber orientation under the bending load. Thus, design concept of a bicycle fork was proposed to secure the safety of a bicycle. The finite element analysis results show that the connection area between a steer tube and a fork blade is critical spot, and 75 or more layers of 0 degree are needed to secure the safety of a bicycle fork.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.605-610
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• 2002

The purpose of this study is to develop an analytic model which can describe the behavior or concrete compressive member strengthened by CFS(Carbon Fiber Sheet) with various cross-sectional shapes such as circular. square, and octagonal and various laminate angles. The failure criterion of laminated CFS is based on Tsai-Wu failure criterion. The stress strain model of confined concrete compressive member is based on an equation proposed by Mander. The effective lateral confining pressure is considered and modified according to various cross-sectional shapes. Octagonal cross-section shows the best results in the aspect of ductility, while circular does in compressive strengthening effects. In addition, [0/0/0/0] laminate in which the direction of fiber is parallel to the direction of principal stress shows the superior strength and ductility than other laminates. The analytic results show that strength and ductility of the analytic model depend on the cross-sectional shapes as well as the laminate angles.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.79-82
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• 2002

A finite element method based on the two-dimensional progressive failure analysis considering material nonlinearity is presented for characterizing the strength and failure of the unidirectional-fabric hybrid laminated composite joints under pin loading. The 8-node laminated shell element is incorporated in the updated Lagrangian formulation. Failure criteria including the Maximum Stress and Tsai-Wu are used in conjunction with the complete unloading stiffness degradation method. For the verification, joint tests are conducted for the specimens with two different ply-number ratios of UD composite to fabric composite. Although there are some differences depending on ply-number ratios, the finite element model using the maximum stress criterion considering nonlinear material behavior predicts the failure strength best.

• 한국산학기술학회논문지
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• 제9권4호
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• pp.853-858
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• 2008

유도가열 전기보온 압력밥솥의 체결 구조는 오븐, 상부 가열판, 체결 링으로 구성되며, 기존의 밥솥과 달리 내부에 압력이 작용하기 때문에 안전성 검토가 반드시 필요하다. 본 연구에서는 유한 요소법을 이용하여 밥솥의 체결 구조인 오븐, 상부 가열판, 체결 링에 대하여 구조해석을 수행하고 구조적으로 안전한 최적 두께를 산출한다. 특히, 오븐은 스테인레스와 알루미늄이 겹쳐서 성형된 제품이므로 복합재료 해석을 수행하고, 안전성 평가를 위하여 von Mises법과 Tsai-Wu법을 도입한다. 오븐과 상부 가열판의 최적 두께 산출을 위하여 설계 변수법을 적용한다.

• Composites Research
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• 제19권6호
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• pp.1-7
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• 2006

본 논문은 수지충전공정을 활용한 상업용 항공기의 복합재 윈도우 프레임을 개발하기 위한 선행 연구이다. 윈도우 프레임을 제작하기 위해 고려중인 2종류의 카본 섬유-triaxial overbraid 와 sleeving braider-에 대해서 VaRTM 공정을 활용한 시편을 제작하고, ASTM 시험법에 따라 물성치를 얻기 위해 물리적/기계적 성질 시험이 실시되었다. 이후 복합재 윈도우 프레임의 최소 플라이수와 무게를 얻기 위해 각각의 탄소 섬유에 대하여 유한요소해석이 수행되었다. 본 연구에서는 구조물의 안전성을 평가하기 위하여 Tsai-Wu 파손강도이론을 사용했다.

• 산업기술연구
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• 제15권
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• pp.217-222
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• 1995

In this paper, the importance of the size effects on the strength ratio is demonstrated by numerical results. The rate of decrease of tensile strength is for glass fiber, based on the experience of a composite manufacturing specialist. For other material, similar procedure may be used until detailed test result on such material is available. The strength criteria used is that of Tsai-Wu for stress space. The factors influencing the ratio are, reducing the tensile strength alone or both tensile and compression strengths, selection of the normalized interaction term, that is, the generalized Von Mises criterion or the Hill's criterion, and the status of applied stresses. Some of the numerical results are presented for a guideline for the furture study.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.179-182
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• 2002

Rapid Prototyping (RP) technologies provide the ability to fabricate initial prototypes from various model materials. Stratasys' Fused Deposition Modeling (FDM) is a typical RP process that can fabricate prototypes out of plastic materials, and the parts made from FDM were often used as load-carrying elements. Because FDM deposits materials in about $300\mutextrm{m}$ thin filament with designated orientation, parts made from FDM show anisotropic material properties. This paper proposes an analytic model to predict the tensile strength of FDM parts. Applying the Classical Lamination Theory, which was developed for laminated composite materials, a computer code was implemented. Tsai-Wu failure criterion was added to the code to predict the failure of the FDM parts. The tensile strengths predicted by the analytic model were compared with experimental data. The data and prediction agreed reasonably well to prove the validity of the model. In addition, a web-based advisory service was developed to provide to strength prediction and design rules for FDM parts.

• Steel and Composite Structures
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• 제7권3호
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• pp.253-262
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• 2007

A methodology to design symmetrically laminated fibre-reinforced structures under transverse loads for minimum weight, with manufacturing uncertainty in the ply angle, is described. The ply angle and the ply thickness are the design variables, and the Tsai-Wu failure criteria is the design constraint implemented. It is assumed that the probability of any tolerance value occurring within the tolerance band, compared with any other, is equal, and thus the approach is a worst-case scenario approach. The finite element method, based on Mindlin plate and shell theory, is implemented, and thus effects like bending-twisting coupling are accounted for. The Golden Section method is used as the search algorithm, but the methodology is flexible enough to allow any appropriate finite element formulation, search algorithm and failure criterion to be substituted. In order to demonstrate the procedure, laminated plates with varying aspect ratios and boundary conditions are optimally designed and compared.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.275-280
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• 2008

To improve the durability of a hydrogen pressure vessel which is applied high-pressure, it needs the autofrettage process which induces compressive residual stress in the Aluminum liner. This study presents the elasto-plastic analysis to predict the behavior of structure accurately, and the Tsai-Wu failure criterion is applied to predict failure of pressure vessel of Aluminum liner and composite materials. Generally, plastic analysis is more complex than elastic analysis and has much time to predict. To complement its weakness, the AxicomPro(EXCEL program), applied radial return algorithm and nonlinear classical laminate theory (CLT), is developed for predicting results with more simple and accurate than the existing finite element analysis programs.